// Copyright (c) 2023 PaddlePaddle Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "paddle/phi/kernels/strided_slice_grad_kernel.h"
#include "paddle/common/flags.h"
#include "paddle/phi/backends/all_context.h"
#include "paddle/phi/core/kernel_registry.h"
#include "paddle/phi/kernels/funcs/strided_utils.h"
#include "paddle/phi/kernels/strided_slice_kernel.h"

COMMON_DECLARE_bool(use_stride_kernel);

namespace phi {

template <typename Context>
void StridedSliceRawGradStridedKernel(const Context& dev_ctx,
                                      const DenseTensor& x,
                                      const DenseTensor& out_grad,
                                      const std::vector<int>& axes,
                                      const IntArray& starts,
                                      const IntArray& ends,
                                      const IntArray& strides,
                                      const std::vector<int>& infer_flags,
                                      const std::vector<int>& decrease_axis,
                                      DenseTensor* x_grad) {
  if (!FLAGS_use_stride_kernel) {
    PADDLE_THROW(common::errors::Fatal(
        "FLAGS_use_stride_kernel is closed. Strided kernel "
        "be called, something wrong has happened!"));
  }
  dev_ctx.Alloc(x_grad, x_grad->dtype());
  x_grad->set_strides(DenseTensorMeta::calc_strides(x_grad->dims()));
  PD_VISIT_ALL_TYPES(x_grad->dtype(), "StridedSliceRawGradStridedKernel", ([&] {
                       phi::StridedTensorFill<data_t>(*x_grad, 0, x_grad);
                     }));
  if (x_grad->numel() == 0) return;
  DenseTensor tmp;
  tmp.set_layout(out_grad.layout());
  tmp.set_lod(out_grad.lod());
  tmp.set_type(out_grad.dtype());
  tmp.Resize(out_grad.dims());
  StridedSliceRawStridedKernel<Context>(dev_ctx,
                                        *x_grad,
                                        axes,
                                        starts,
                                        ends,
                                        strides,
                                        infer_flags,
                                        decrease_axis,
                                        &tmp);
  PD_VISIT_ALL_TYPES(
      out_grad.dtype(), "StridedSliceRawGradStridedKernel", ([&] {
        phi::StridedTensorCopy<data_t>(
            out_grad,
            common::vectorize<int64_t>(tmp.dims()),
            common::vectorize<int64_t>(tmp.strides()),
            tmp.offset(),
            &tmp);
      }));
}

template <typename Context>
void StridedSliceGradStridedKernel(const Context& dev_ctx,
                                   const DenseTensor& x,
                                   const DenseTensor& out_grad,
                                   const std::vector<int>& axes,
                                   const IntArray& starts,
                                   const IntArray& ends,
                                   const IntArray& strides,
                                   DenseTensor* x_grad) {
  if (!FLAGS_use_stride_kernel) {
    PADDLE_THROW(common::errors::Fatal(
        "FLAGS_use_stride_kernel is closed. Strided kernel "
        "be called, something wrong has happened!"));
  }
  std::vector<int> infer_flags(axes.size(), 1);
  std::vector<int> decrease_axis;
  StridedSliceRawGradStridedKernel<Context>(dev_ctx,
                                            x,
                                            out_grad,
                                            axes,
                                            starts,
                                            ends,
                                            strides,
                                            infer_flags,
                                            decrease_axis,
                                            x_grad);
}

}  // namespace phi

PD_REGISTER_KERNEL_FOR_ALL_BACKEND_DTYPE(
    strided_slice_raw_grad, STRIDED, phi::StridedSliceRawGradStridedKernel) {}

PD_REGISTER_KERNEL_FOR_ALL_BACKEND_DTYPE(strided_slice_grad,
                                         STRIDED,
                                         phi::StridedSliceGradStridedKernel) {}
